Debris flows and shallow landslides are highly mobile liquefied landslides containing a variety of materials from fine particles to large boulders and tree branches. They are caused by excessive water on and within slopes, caused by rainfall, glacier melt or similar. The likelihood of debris flows is increased when vegetation and other surface protection have been removed from vulnerable slopes, perhaps by wildfire or clearance.
Maccaferri® debris flow fences or ring nets act to catch landslide material to protect infrastructure below, and are positioned within the path of the shallow landslide, often in natural gullies, channels or chutes on the slope.
Depending on the slope and where these structures are installed, debris flow fences can be broadly categorised into two categories or a combination between the two types:
- Open slope or shallow landslide
Open slope type debris flow fences are similar to rockfall barriers (catch fences) but may incorporate variations such as additional longitudinal ropes or larger rope diameters, additional energy absorption elements, reduced post spacing and variable geometries depending on the impact assessment.
In addition, combinations of different diameter ring nets are often used as the containment mesh. Ring nets are ideal in these structures as they have excellent energy and pressure absorption capacity whilst undergoing deformation, before loads are transferred to the compression brakes.
Channel debris flow fences are custom made to suit specific gully dimensions. Longitudinal ropes with intercepting panels are installed across the gully with anchors installed into the side slopes. Sometimes this can also be a combination of utilising a post on one side of the fence and butt against the side slopes on another. For this reason, accurate dimensioning of the gully is important for the design and manufacturing of the fence.
WHY CHOOSE MACCAFERRI DEBRIS FLOW FENCE?
- Optimised ring net design provides a balance of strength, weight and flexibility
- Incorporates specific energy absorption elements to restrain the flow
- Designed to be in place as a barrier until vegetation in the up-slope triggering zone is re-established on the vulnerable slopes above and the risk of another debris flow event has been identified to be minimal or mitigated
- Saves traffic disruption where he arrested volume of debris can be removed in stages while allowing use of the road or rail line
- Quick and easy to install; it can be removed leaving the foundation intact and reinstalled if risks from debris flows increase in the future
- Can be customised to suit the dimensions of the project, the anticipated debris material and the expected volume of the flow - a preliminary assessment and design suggestion can be prepared for your project requirements